Method for Manufacturing a Part Consisting at Least Partially of a Metal Alloy, and Optimisation Method

ABSTRACT

The present invention concerns a method for manufacturing a part consisting at least partially of a metal alloy. The method includes a metallurgical manufacturing step a1) consisting of manufacturing the body of the part. The method subsequently includes a reinforcing step a2) consisting of forming a local reinforcement directly on the body, in an area of the part that is under stress. The invention also concerns a method for optimising a part.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a manufacturing method for a partconstituted at least partially of a metal alloy. The invention alsorelates to an optimization method for a part.

The field of the invention is that of manufacturing of parts constitutedin whole or in part of a metal (ferrous or nonferrous) alloy, where saidmanufacturing includes successive foundry and forge operations.

BACKGROUND OF THE INVENTION

Saint-Jean Industries developed the COBAPRESS (trademark) method foraluminum and alloys thereof over 30 years ago. This technology consistsof forging a foundry preform in a single forge operation, as describedin particular in the documents EP0119365, EP0586314 and EP2877353.

The COBAPRESS method has proven to be very effective in suspensionapplications at most automobile manufacturers. In particular, comparedwith the conventional foundry, a notable improvement of the mechanicalproperties and especially decrease assistance is possible with thismethod. Also, this method is competitive compared to the forge in termsof costs and achievable geometric complexity.

EP0586314 describes the positioning of inserts in a foundry preform andthen striking the preform to get the final part. The inserts are fixedlyand permanently integrated by deformation of the material, thus defininglocally reinforced areas. The inserts are formed aside and then addedonto the body of the part constituted by the preform; that is what thepresent invention aims to avoid.

Today reducing the weight of structures, in the automotive, aeronauticand industrial fields, is a necessity connected to developments insafety, environmental and other standards.

The weight objectives for structures are perpetually decreasing with anincrease of the stresses thereon and a cost objective compatible withthe market. In the majority of cases today, these constraints lead to acompromise involving the choice of materials, processes, weights andcosts.

As an example, if a particular area of the part is subject to largestresses, the material for this part overall is going to be driven bythis area and lead to higher costs related to the choice of thismaterial.

SUMMARY OF THE INVENTION

The objective of the present invention is to propose an improvedmanufacturing method.

In this regard, the invention concerns a manufacturing method for a partconstituted at least partially of a metal alloy, wherein the methodcomprises a metallurgical manufacturing step a1) consisting ofmanufacturing the body of the part, characterized in that the methodnext comprises a reinforcement step a2) consisting of forming a localreinforcement on the body, in an area under stress of the part.

Thus, the mechanical properties of the part, for example the fatigueresistance or hardness thereof can be locally improved with theinvention, while keeping the mass of the reinforced part the lowestpossible and without using a part that is added on. As an alternative ora complement, a section of the part can be reduced locally because ofthe invention resulting in space savings. Further, the overallperformance of the part, for example the stiffness thereof, can beimproved with the invention.

According to a first embodiment, the metallurgical manufacturing stepa1) comprises a foundry operation a11) consisting of manufacturing afoundry preform, and then a forge operation a12) consisting of forgingthe foundry preform to obtain the body of the part. This metallurgicalmanufacturing step a1) corresponds to the implementation of theCOBAPRESS method.

According to a second embodiment, the metallurgical manufacturing stepa1) includes a foundry operation a11) consisting of manufacturing thebody of the part. This foundry operation a11) is not followed by a forgeoperation a12).

According to a third embodiment, the metallurgical manufacturing stepa1) includes a forge operation a12) consisting of manufacturing the bodyof the part. This forge operation a12) is not preceded by a foundryoperation a11).

The invention also concerns a method for optimization of the design ofan existing part, comprising a metal alloy body, wherein theoptimization method comprises the following successive phases:

b1) identify an area under stress of the existing part, for example bynumerical simulation;

b2) define an optimized part comprising a modified body, by providing atleast one local reinforcement formed on the body in the stressed area;

b3) define metallurgical manufacturing tools conforming to the body ofthe optimized part;

b4) manufacture the body of the optimized part with the tools;

b5) form a local reinforcement directly on the body, in the area of theoptimized part under stress.

According to other advantageous features of the invention, consideredalone or in combination:

-   -   The part is a structural part for car (in particular a part for        pivot type suspension, direction arm, suspension arm, under        frame structural part, etc.), aeronautic, industrial equipment        or medical device.    -   The local reinforcement has a surface arranged at least 50% in        contact with the body of the part.    -   The local reinforcement substantially marries the body of the        part.    -   Several local reinforcements are formed on the body, in one or        more areas under stress of the part.    -   The method comprises a step of preparation of the surface of the        area to be reinforced, between the metallurgical manufacturing        step a1) and the reinforcement step a2).    -   The method comprises a step of finishing the part in the        reinforced area, after the reinforcement step a2).    -   The method comprises a step of surface treatment, applied at        least on a portion of the body, between the steps a1) and a2).    -   The method comprises a step of surface treatment, applied at        least on a portion of the part, after step a2).    -   The body and the local reinforcement are made of different metal        alloys.    -   The body is made of a metal alloy, whereas the local        reinforcement is made of a composite material.    -   The body is made of a metal alloy, whereas the local        reinforcement is made of a ceramic material.    -   The local reinforcement is formed by cold spraying.    -   The local reinforcement is formed by micro-arc oxidation.    -   The local reinforcement is formed by adhering a composite        assembly taking the final shape thereof on the body of the part.    -   The local reinforcement is formed by baking a resin.    -   The local reinforcement is formed by additive manufacturing.    -   The local reinforcement is substituted for an original portion        of the body of the existing part.    -   The local reinforcement is substituted for an insert fitted,        overmolded or pressed on the body of the existing part.    -   The optimized part has substantially the same dimensions as the        existing part.    -   The optimized part has dimensions that are locally reduced        compared to the existing part.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood upon reading the followingdescription, given solely as a non-limiting example, and made withreference to the accompanying figures wherein:

FIG. 1 is a top view of a part conforming to the state of the art,comprising a metal alloy body, manufactured according to a foundryoperation and then a forge operation;

FIG. 2 is a side view of the part from FIG. 1;

FIGS. 3 and 4 are views analogous to FIGS. 1 and 2 showing anoptimization method for the design of the part;

FIGS. 5 and 6 are views analogous to FIGS. 1 and 2 showing a partoptimized according to the invention, comprising local reinforcementsformed on the body in stressed areas;

FIG. 7 is a section along the line VII-VII in FIG. 6; and

FIGS. 8 to 12 are views analogous to FIGS. 3 to 7 showing a secondembodiment of a part optimized according to the invention.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

A part 10 is shown in FIGS. 1 to 4 comprising a single piece body 11 anda tubular insert 18 fitted in the body 11. As an example, part 10 is acar suspension part.

The body 11 is made of a metal alloy, for example aluminum alloy,according to two successive foundry and forge operations. The body 11comprises a main portion 12, an end portion 13 and a long portion 14connecting the portions 12 and 13. Two through openings 15 and 16 arearranged in the portion 12. The opening 15 has a substantiallyrectangular section, whereas the opening 16 has a circular section.

The insert 18 is made of metal alloy, for example steel, and thenfitted, overmolded or pressed (in particular by COBAPRESS) in theopening 16 formed in the body 11. The insert 18 provides variousfunctions between the body 11 and an element not shown arranged throughthe opening 16: thermal connection, friction resistance, lubrication,etc.

Areas under stress Z4, Z5 and Z6 of part 10, corresponding respectivelyto elements 14, 15 and 16, are shown in FIGS. 3 and 4.

In the context of the present invention, an area under stress of part 10is defined as being an area subject to large mechanical, thermal,friction and/or abrasion stresses when the part 10 is in service. Thesestresses are called large, in so far as they require specific attentionfor preserving the operating integrity of the part because of theenvironment thereof (mechanical system in which the part isincorporated, external factors, etc.).

As examples:

-   -   The mechanical stresses can be caused by forces of flexion,        torsion, traction and/or compression experienced by this area;    -   The thermal stresses can be caused by a permanent or temporary        local temperature increase experienced by this area;    -   The frictional constraints caused by an electric cable which        extends along the part and which could rub against the surface        of the part in this area;    -   The abrasion constraints can be caused by spraying of materials        against this area from the ground on which the car equipped with        the part is traveling.

In practice, the areas Z4, Z5 and Z6 of the part 10 are not subject tothe same stresses in service.

In the area Z4, reduced weight of the portion 14 made of metal alloy issought without reducing the mechanical performance thereof. For thispurpose, an external portion 140 of this portion 14 can be replaced by acomposite material.

In the area Z5, improved resistance of the part 10 is sought in the areaof the opening 15 without changing the material making up the body 11.For this purpose, a portion 150 located around the opening 15 can bereplaced by a metal alloy that is more resistant than that of the body11.

In area Z6, reduced weight of the portion 12 is sought without reducingthe performance of the part 10 in the area of the opening 16. For thispurpose, the steel insert 18 can be replaced by a covering formed in theopening 16 by cold spraying of a powder comprising metal particles(alloys of aluminum, copper, cobalt, nickel, molybdenum, aluminumquasi-crystals, etc.).

Of course, other solutions can be selected depending on thespecifications document to be satisfied.

A part 20 according to the invention is shown in FIGS. 5 to 7. The part20 is an optimized version of the part 10 shown in FIGS. 1 to 4. Thepart 20 has a function and dimensions similar to the part 10.

Some constituent elements of the part 20 are comparable to those of part10 described above and, for purposes of simplification, bear the samenumeric references. Other constituent elements of the part 20 havedifferences from the part 10 and have numeric references increased by10.

The part 20 comprises a body 21, and also various local reinforcements40, 50 and 60 formed directly on the body 21, respectively in areas Z4,Z5 and Z6 of part 10.

As mentioned before, these areas Z4, Z5 and Z6 are not subject to thesame stresses in service. Under these conditions, the choice ofmaterials constituting the body 21 and the local reinforcements 40, 50and 60 is a compromise in terms of performance, weight and cost.

The body 21 is made of a metal alloy, for example aluminum alloy,according to two successive foundry and forge operations. The body 21comprises a main portion 22, an end portion 13 and a long portion 24connecting the portions 22 and 13. Two through openings 15 and 16 arearranged in the portion 22.

In the area Z4, the body 21 includes a long portion 24 provided as localreinforcement 40. The portion 24 is made of metal alloy, while thereinforcement 40 is made of composite material. For example, thereinforcement 40 is formed by layers of carbon, glass or thermoplastic(in particular poly(p-phenyleneterephtalamide) known under the brandname Kevlar) fibers, precoated with resin, having a nearly finishedstate. The reinforcement 40 comes in the form of a composite elementadhered onto the body 21 and taking its final shape directly on the body21. The reinforcement 40 is substituted for the portion 140 of the body11 such that the portions 14 and 24 have substantially the samedimensions. With the reinforcement 40, the part 20 can be made lighterin the area Z4 without reducing the mechanical performance thereof.

In the area Z5, a reinforcement 50 is substituted for the portion 150 ofthe body 11. The opening 15 is formed through this reinforcement 50 inthe portion 22. The opening 15 has the same dimensions for the parts 10and 20. The reinforcement 50 is made of stronger metal alloy than thatof the body 11, for example by cold spraying. The strength of the part20 is improved near the opening 15 compared to the part 10, withoutchanging the material of the body 21 compared to the body 11.

In area Z6, the insert 18 is replaced by a coating 60 formed by coldspraying in the opening 16. The portion 22 of the part 20 can be madelighter with the coating 60 without reducing the performance thereofnear the opening 16.

The body 21 makes up the majority of the volume of the part, incomparison with the reinforcements 40, 50 and 60.

A variant of part 10 from FIGS. 3 and 4 is shown in FIGS. 8 and 9. Areasunder stress Z4 and Z6 of part 10, corresponding respectively toelements 14 and 16, are shown in this variant. In the zone Z4, twoexternal portions 141 and 142 of the portion 14 can be replaced by acomposite material. In area Z6, the steel insert 18 can be replaced by acoating formed by cold spraying in the opening 16.

A part 30 according to the invention is shown in FIGS. 10 to 12. Thepart 30 is an optimized version of the part 10 shown in FIGS. 8 and 9.The part 30 has a function and dimensions similar to the part 10.

Some constituent elements of the part 30 are comparable to those of part10 described above and, for purposes of simplification, bear the samenumeric references. Other constituent elements of the part 30 havedifferences from the part 10 and have numeric references increased by10.

The part 30 comprises a body 31, and also various local reinforcements41, 42 and 60 formed directly on the body 31.

The body 31 is made of a metal alloy, for example aluminum alloy,according to two successive foundry and forge operations. The body 31comprises a main portion 12, an end portion 13 and a long portion 34connecting the portions 32 and 13. Two through openings 15 and 16 arearranged in the portion 12.

In the area Z4, the body 31 includes a long part 34 provided with thetwo local reinforcements 41 and 42. The part 34 is made of metal alloy,while the reinforcements 41 and 42 are made of composite material. Thereinforcements 41 and 42 are substituted for the respective portions 141and 142 of the body 11 such that the portions 14 and 34 havesubstantially the same dimensions. With the reinforcements 41 and 42,the part 30 can be made lighter in the area Z4 without reducing themechanical performance thereof.

In area Z6, the insert 18 is replaced by the coating 60 formed by coldspraying in the opening 16. The portion 22 of the part 20 can be madelighter with the coating 60 without reducing the performance thereofnear the opening 16.

Moreover, the part 10/20/30 can be shaped differently than in FIGS. 1 to12 without departing from the scope of the invention.

In the examples from FIGS. 5 to 7 and 10 to 12, each of thereinforcements 40/41/42/50/60 marries the body 21/31 of the part 20/30.In other words, each of the reinforcements 40/41/42/50/60 has a surfacearranged completely in contact with the body 21/31.

As a variant not shown, the surface of the reinforcement in contact withthe body can be arranged at least 50% in contact with the body (and upto 100%). Preferably, the surface of the reinforcement is arranged atleast 90% in contact with the body.

Whatever the embodiment of the invention, the part 20/30 is at leastpartially constituted of a metal alloy and includes:

-   -   a metal alloy body 21/31 manufactured by a metallurgical        manufacturing step a1); and    -   at least one local reinforcement formed directly on the body        21/31 in an area under stress of the part 20/30 during a        reinforcement step a2) subsequent to the metallurgical        manufacturing step a1).

The body 21/31 constitutes most of the volume of the part 20/30 incomparison with the reinforcements. The body 21/31 could be constitutedof one functional part all alone, whereas the characteristics of thispart can be locally improved by the reinforcements. Each reinforcementhas a volume that is less than 20% of the volume of the body 21/31 andpreferably less than 10%.

In the context the invention, the local reinforcement can be formed bycold spray, micro-arc oxidation, additive manufacturing, baking of aresin in a mold, adhering a composite assembly (which takes the finalshape thereof on the body of the part when the adhesive dries), or anyother suitable technique.

The invention excludes reinforcement by parts added onto the body, forexample by welding, screwing or pressing.

The invention also excludes reinforcement parts integrated with the bodyby overmolding.

A goal the invention is also a manufacturing method for a part 20/30constituted at least partially of a metal alloy.

The method comprises the following successive steps a1) and a2):

a1) a metallurgical manufacturing step consisting of manufacturing thebody 21/31 of the part 20/30; and

a2) a reinforcement step consisting of forming a local reinforcementdirectly on the body 21/31, in an area under stress of the part 20/30.

According to a first embodiment, the step a1) comprises a foundryoperation and then a forge operation, according to the COBAPRESS method.

According to a second embodiment the step a1) includes only a foundryoperation.

According to a third embodiment the step a1) includes only a foundryoperation.

The method can comprise a step of preparation of the surface of the areato be reinforced, between the steps a1) and a2), depending on thetechnique used in step a2). As nonlimiting examples, this surfacepreparation step can include brushing, degreasing, shot blasting,machining or depositing. In the case of a composite reinforcement, thedepositing can consist of applying an adhesive on the body 21/31 of thepart 20/30.

The method can also comprise a step of finishing the part 20/30 in thereinforced area, after the reinforcement step a2). As nonlimitingexamples, this finishing step may include machining, polishing orsurface treatment.

The method can also include a surface treatment step. The surfacetreatment can be applied at least on a portion of the body 21/31 betweensteps a1) and a2), or at least on a portion of the surface of the partafter step a2).

The invention also concerns a method for optimization of the design ofan existing part 10, comprising a metal alloy body 11. Initially, thisbody 11 is made for example following a foundry operation and or a forgeoperation.

The optimization method comprises the following successive phases b1,b2, b3, b4 and b5:

b1) Identify one or more stressed areas Z4/Z5/Z6 of the existing part10, for example by numerical simulation.

b2) Define an optimized part 20/30 comprising a modified body 21/31, byproviding at least one local reinforcement 40, 41, 42, 50 and/or 60formed on the body 21/31 in the stressed area Z4/Z5/Z6.

b3) Define metallurgical manufacturing tools (generally foundry and/orforge) for manufacturing the body 21/31 of the optimized part 20/30. Themanufacturing tools for the body 21/31 of the part 20/31 are differentfrom the manufacturing tools for the original body 11 of the part 10. Insome cases, the foundry molds and forge mother molds that had been usedfor manufacturing the body 11 can be simply modified to be used formanufacturing the body 21/31.

b4) Manufacture the body 21/31 of the optimized part 20/30 with thetools. This phase may include a foundry operation and then a forgeoperation, according to the implementation of the COBAPRESS method.Alternatively, this phase can include only a foundry operation.

b5) Form the local reinforcement 40, 41, 42, 50, 60 directly on the body21/31, in the area under stress Z4/Z5/Z6 of the optimized part 20/30.

The technical characteristics of the various embodiments and variantsmentioned above can be, in whole or for some of them, combined with eachother. Thus, the part 20/30 may be adapted in terms of cost,functionality and performance.

1. A manufacturing method for a part constituted at least partially of ametal alloy, wherein the method comprises a metallurgical manufacturingstep a1) consisting of manufacturing the body of the part, wherein themethod next comprises a reinforcement step a2) consisting of forming alocal reinforcement directly on the body, in an area under stress of thepart.
 2. The method according to claim 1, wherein the metallurgicalmanufacturing step a1) comprises a foundry operation a11) consisting ofmanufacturing a foundry preform, and then a forge operation a12)consisting of forging the foundry preform to obtain the body of thepart.
 3. The method according to claim 1, wherein the metallurgicalmanufacturing step a1) comprises a foundry operation a11) or a forgeoperation a12) consisting of manufacturing the body of the part.
 4. Themethod according to claim 1, wherein the local reinforcement has asurface arranged at least 50% in contact with the body of the part. 5.The method according to claim 1, wherein the local reinforcementsubstantially marries the body of the part.
 6. The method according toclaim 1, wherein several local reinforcements are formed on the body, inone or more areas under stress of the part.
 7. The method according toclaim 1, further comprising a step of preparation of the surface of thearea to be reinforced, between the metallurgical manufacturing step a1)and the reinforcement step a2).
 8. The method according to claim 1,further comprising a step of finishing the part in the reinforced area,after the reinforcement step a2).
 9. The method according to claim 1,wherein the body and the local reinforcement are made of different metalalloys.
 10. The method according to claim 1, wherein the body is made ofa metal alloy, whereas the local reinforcement is made of a compositematerial.
 11. The method according to claim 9, wherein the localreinforcement is formed by cold spraying.
 12. The method according toclaim 9, wherein the local reinforcement is formed by micro-arcoxidation.
 13. The method according to claim 10, wherein the localreinforcement is formed by adhering a composite assembly taking thefinal shape thereof on the body of the part.
 14. The method according toclaim 10, wherein the local reinforcement is formed by baking a resin.15. The method according to claim 1, wherein the local reinforcement isformed by additive manufacturing.
 16. A method for optimization of thedesign of an existing part, comprising a metal alloy body, wherein theoptimization method comprises the following successive phases: b1)identifying an area under stress of the existing part; b2) defining anoptimized part comprising a modified body, by providing at least onelocal reinforcement formed on the body in the stressed area; b3)defining metallurgical manufacturing tools conforming to the body of theoptimized part; b4) manufacturing the body of the optimized part withthe tools; and b5) forming the local reinforcement directly on the body,in the area under stress of the optimized part.
 17. The method accordingto claim 16, wherein the local reinforcement is substituted for anoriginal portion of the body of the existing part.
 18. The methodaccording to claim 16, wherein the local reinforcement is substitutedfor an insert fitted, overmolded or pressed on the body of the existingpart.
 19. The method according to claim 13, wherein the localreinforcement is formed by baking a resin.